mqtt: Fix incorrect reads on error; Update ping processing
mqtt: Fix incorrect reads on error; Update ping processing

* Update submodule: git log --oneline 4874bab35659bd2301e65fd849f6559d7380d4f1..64f88b4412ea6649dbf207a07370c2617160d044

Detailed description of the changes:
* Fix documentation of config struct
  - See merge request espressif/esp-mqtt!129
  - See commit https://github.com/espressif/esp-mqtt/commit/e31834c
* Changes the moment we update keepalive_tick.
  - See merge request espressif/esp-mqtt!127
  - See commit https://github.com/espressif/esp-mqtt/commit/2c2e6f3
* MQTT: Fix signature matching for some integer values
  - See merge request espressif/esp-mqtt!128
  - Closes https://github.com/espressif/esp-idf/issues/8482
  - MQTT: Fix signature matching for integer values (espressif/esp-mqtt@6b794e4)
* Make the mqtt submodule logging tags lower case
  - See merge request espressif/esp-mqtt!122
  - See commit https://github.com/espressif/esp-mqtt/commit/fb3184c

Closes https://github.com/espressif/esp-idf/issues/8482
Closes https://github.com/espressif/esp-idf/issues/8550

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf